(1) Technical Field
The present invention relates generally to timepieces and more particularly to timepieces having a linear scale, wherein the passage of time is represented by the rising or falling of a fluid column.
(2) Related Art
Various timepieces having linear scales are known in the art. For example, U.S. Pat. No. 5,331,609 to Gubin and U.S. Pat. No. 3,875,736 to Gulko describe timepieces having linear scales and belt-driven, non-fluid indicators. U.S. Pat. Nos. 3,783,598 to Parr and 4,262,348 to Hess describe timepieces having fluid-filled tubes adjacent a linear scale, wherein movement of fluid within the tubes represents the passage of time. Each of these devices, however, suffers from the deficiency that they can be read from a maximum of two positions (i.e., a position facing the time scale and possibly a second position opposite the first) and can often only be read from one position. In addition, the Parr device must utilize piston pumps that are small enough so as not to make the device too large to be useful. In order to utilize the smaller fluid reservoir of these piston pumps, the fluid-filled tubes of the Parr device must be thin capillary tubes. The size of these tubes further reduces the readability and utility of the Parr device.
United Kingdom Patent Application 2,371,833 to Coleman describes a device having two concentric, clear, fluid-filled tubes in which the heights of dynamic vortices formed within the tubes represent the passage of time. Such a device requires a great deal of energy, particularly in the formation of the vortices, and is therefore impractical for use as a personal timepiece. Furthermore, this device requires a large base-mounted or external sump for fluid transfers. Accordingly, there is a need in the art for a timepiece having a linear scale, wherein the disadvantages of the prior art devices above are avoided.